The U.S. Food and Drug Administration has approved Biogen Inc's drug for treating an inherited form of amyotrophic lateral sclerosis (ALS), the health regulator said on Tuesday.

The drug, branded as Qalsody, got a green light under the agency's accelerated approval pathway that allows for speedy access to treatments which target serious and life-threatening conditions, making it the first available therapy for genetic ALS.

The drug's approval is based on data that showed it reduced levels of neurofilament protein, which is an indicator of nerve cell degeneration that is believed to be tied with progression of the symptoms of the disease.

The company will be required to provide more data on the drug's effectiveness for it to remain on the market and for the FDA to grant full traditional approval.

A panel of FDA experts in March voted in favor of an accelerated approval, but the same panel voted that data from trials of the drug did not support full approval.